Posted: Tue May 23, 2017 10:04 pm Post subject: Re: when to use a gerund?

rayt wrote:

Below is a question I have encountered recently..

The owner of Print Depot personally wrote a letter _______ for the typo that appeared on the law firm’s brochures.

a. has apologized
b. apologizes
c. apologizing
d. will apologize

could please advise me why C. APOLOGIZING is the answer here??

Thank you.

You could also say the owner "wrote a letter which apologized for the typo." It seems to me that "apologizing" replaces the "which apologized". I'm sorry I don't remember the official grammar names. Perhaps someone else will explain it further.